If you're behind a firewall, either software or hardware (router) you're pretty safe. Hackers generally don't want to waste any time on a home computer, they want more valuable things. Mine runs 24/7 and has for about 3 years. Constantly uploading data every 4-5 seconds, several pages every couple of minutes, data to my SQL Server every minute, constantly streaming webcam, and much more... so lots of stuff going on all the time. I only leave a few ports open on my router so there isn't a whole lot someone can do even if they tried.